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1,2‐Addition of transient W(CO)5‐complexed phosphinidenes exoto hexamethyl Dewar benzene affords the novel 3‐phosphatricyclo[3.2.0.02,4]hept‐6‐ene complexes. The fused tricyclic phosphiranes are obtained as both the Zand the thermally less stable Eisomers, the 31P NMR chemical shifts of which differ by about 60 ppm. A computational investigation shows that the phosphorus pyramidalization and the presence of the γ double bond are responsible for this effect. The semiquantitative results contribute to a more systematic understanding of the structural influences on 31P chemical shieldings. The congested double bond of the Zisomer can be epoxidized with m‐chloroperbenzoic acid (MCPBA) to afford a fused tetracyclic P,O bis‐adduct.

Intramolecular phosphinidene addition to the CC bond of Mo‐complexed, seven‐membered phosphorus heterocycles affords three novel [(diphos)Mo(CO)4] complexes (18–20). The three bidentate phosphorus baskets differ in the composition of the seven‐membered ring: one of the phosphorus atoms is flanked by CH2, NCH3, or O. The unsaturated tetrahydrophosphepine precursors are synthesized by either ring‐closing metathesis (C and N derivatives) or by a cyclization sequence (O derivative). The crystal structures of the nitrogen‐ (19) and oxygen‐containing (20) baskets have relatively small P‐Mo‐P angles of 76.240(13)° and 77.626(12)°, respectively, and complex 20has slightly shortened MoP bond lengths.

Novel, highly stable, linear and branched mono‐ and diphospha[n]triangulanes were synthesized in high yields by the CuCl‐catalyzed phosphinidene addition to spirocyclopropanated methylenecyclopropanes and bicyclopropylidenes. The effect of spirofusion on the electronic properties of these esthetically attractive phosphacycles is apparent from X‐ray single crystal structure analyses, which reveals a tightening of the phosphirane ring on additional spirocyclopropanation, and from the NMR features that show deshielded chemical shifts for the ring‐phosphorus and ‐carbon atoms. Steric factors play a role in the addition reaction when the substrate alkene carries a second sphere of spirocyclopropane rings and causes the formation of 2‐phosphabicyclo[3.2.0]heptenes in small amounts. These by‐products most probably result from addition of the [PhP(Cl)W(CO)5]‐Cu‐L (L=alkene or solvent) reagent to the spirocyclopropanated bicyclopropylidene to give an intermediate σ‐complex, which subsequently, facilitated by steric factors, undergoes a cyclopropylcarbinyl to cyclobutyl ring expansion followed by a [1,3]‐sigmatropic shift.

Reaction of the transient phosphinidene complexes R‐PW(CO)5with N‐substituted‐diphenylketenimines leads unexpectedly to the novel 2‐aminophosphindoles, as confirmed by an X‐ray crystal structure determined for one of the derivatives. Experimental evidence for a methylene‐azaphosphirane intermediate was found by using the iron‐complexed phosphinidene iPr2N‐PFe(CO)4, which affords the 2‐aminophosphindole together with the novel methylene‐2,3‐dihydro‐1H‐benzo[1,3]azaphosphole. Analysis of the reaction pathways with DFT indicates that the initially formed methylene‐azaphosphirane yields both phosphorus heterocycles by way of a [1,5]‐ or [1,3]‐sigmatropic shift, respectively, followed by a H‐shift. Strain underlies both rearrangements, which causes these remarkably selective conversions that can be tuned by changing the substituents.

The synthesis of highly strained bicyclic phosphirane and phosphirene iron–tetracarbonyl complexes, that is, complexes with 2‐aza‐1‐phosphabicyclo[n.1.0]alkanes and ‐alkenes (n=3–5), is explored by using intramolecular cycloaddition of an in situ generated electrophilic phosphinidene complex, [R(iPr)NPFe(CO)4], to its CC‐ and CC‐containing R substituent. Saturated bicyclic complexes 7 a–cwith n=4–2 are remarkably stable, as illustrated by the X‐ray crystal structure for 7 b(n=3), yet all readily undergo retroaddition to react with phenylacetylene. Shuttling of the phosphinidene iron complex between two equivalent CC groups is demonstrated for a 1‐butene‐substituted 2‐aza‐1‐phosphabicyclo[3.1.0]hexane by selective 1H NMR magnetization transfer from the phosphirane protons to the olefinic protons. Even the more strained unsaturated bicycles 17 a,b(n=4,3) are surprisingly stable as illustrated by the X‐ray crystal structure for 17 a(n=4), but the smaller phosphabicyclo[3.1.0]hex‐5‐ene (17 c, n=2) dimerizes to tricyclic 19with a unique ten‐membered heterocyclic ring; an X‐ray crystal structure is reported. Like their saturated analogues also the bicyclic phosphirenes readily undergo retroaddition as shown by the reaction of their phosphinidene iron moiety with phenylacetylene.

Reaction of electrophilic phosphinidene complex [MePW(CO)5] with 1,6‐methano‐[10]annulene results in the sole formation of the isomeric CC insertion products 6 c(main) and 6 d(minor). The single‐crystal X‐ray structure of the complexed 1,7‐methano‐3‐phospha[11]annulene (6 c) shows a syn‐W(CO)5group at the exobent phosphorus. The structure displays CC bond alternation without bonding between the bridgehead carbon atoms. Density functional theory calculations indicate 6 cto result from a concerted disrotatory ring opening of an undetected tricyclic exo–synphosphirane intermediate. The endo–antiphosphirane cannot undergo ring expansion, due to the high barrier that is associated with an intramolecular antara–antararetro Diels–Alder reaction. The stabilizing effect of transition‐metal coordination is discussed.

The properties of the 16‐electron phosphinidene complex [CpRIrPR] were investigated experimentally and theoretically. Density functional theory calculations show a preferred bent geometry for the model complex [CpIrPH], in contrast to the linear structure of [CpIrNH]. Dimerization to give [{CpIrPH}2] and ligand addition to afford [Cp(L)IrPH] (L=PH3, CO) were calculated to give compounds that were energetically highly favorable, but which differed from the related imido complexes. Transient 16‐electron phosphinidene complex [Cp*IrPAr] could not be detected experimentally. Dehydrohalogenation of [Cp*IrCl2(PH2Ar)] in CH2Cl2at low temperatures resulted in the novel fused‐ring systems 17(Ar=Mes*) and 20(Ar=Mes), with dimeric [{Cp*IrPAr}2] being the likely intermediate. Intramolecular CH bond activation induced by steric factors is considered to be the driving force for the irreversible formation of 17and 20. ONIOM calculations suggest this arises because of the large steric congestion in [{Cp*IrPAr}2], which forces it toward a more reactive planar structure that is apt to rearrange.

Reaction of an in situ generated phosphinidene complex [PhPW(CO)5] with the aromatic azulene and guaiazulene leads to unexpected 1,4‐adducts of the seven‐membered ring and to CH bond insertion of the five‐membered ring. A DFT analysis suggests that the reaction is initiated by formation of a η1‐complex between the phosphinidene and the five‐membered ring of the aromatic substrate. Four conformations of this complex were identified. Two convert without barrier to the slightly more stable syn‐and anti‐1,2‐adducts. These undergo pericyclic 1,7‐sigmatropic rearrangements with remarkably low barriers to give 1,4‐adducts, with an inverted configuration at the phosphorus center. An X‐ray crystal structure is presented for one of the 1,4‐adducts of guaiazulene. The other two η1‐complexes insert with modest barriers into a CH bond of the five‐membered ring.

The novel phosphinidene complex [Cp*(NHC)Ir&dbond;PMes*] (3; NHC=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) was prepared in high yield from [Cp*(NHC)IrCl2] (2) and [LiPHMes*]·3 THF. It represents the first example of an NHC ligated transition metal phosphinidene complex. The X-ray crystal structure for 3 is also reported. DFT calculations on the N-heterocyclic carbene containing parent complexes [Cp(NHC)Ir&dbond;E] (E=PH, NH, CH2) show that the NHC ligand acts as good σ-donor/weak π-acceptor ligand and forms strong Ir&bond;C(NHC) single bonds. The Ir&dbond;E double bonds result from strong triplet–triplet interactions between [Cp(NHC)Ir] and E.

The novel phosphinidene complex [Cp*(NHC)IrPMes*] (3; NHC=1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene) was prepared in high yield from [Cp*(NHC)IrCl2] (2) and [LiPHMes*]⋅3 THF. It represents the first example of an NHC ligated transition metal phosphinidene complex. The X‐ray crystal structure for 3is also reported. DFT calculations on the N‐heterocyclic carbene containing parent complexes [Cp(NHC)IrE] (E=PH, NH, CH2) show that the NHC ligand acts as good σ‐donor/weak π‐acceptor ligand and forms strong IrC(NHC) single bonds. The IrE double bonds result from strong triplet–triplet interactions between [Cp(NHC)Ir] and E.

Novel, very stable ruthenium and osmium containing terminal phosphinidene complexes [(η6‐Ar)(L)MPMes*] (Ar=benzene, p‐cymene; L=PR3, CO, and RNC) have been prepared by dehydrohalogenation of novel [(η6‐Ar)MX2(PH2Mes*)] complexes in the presence of a stabilizing ligand. Xray crystal structures are reported for [(η6‐C6H6)(PPh3)RuPMes*] (9) and [(η6‐pCy)(PPh3)OsPMes*] (4). Dehydrohalogenation in the absence of a stabilizing ligand resulted in the new Pspiroannulated Ru2P2‐ring structure 16. Dehydrohalogenation in the presence of but‐2‐yne gave a novel phosphaallyl complex [(η6‐Ar)Ru(η3‐R2PC(Me)CHMe)] 26, for which an Xray crystal structure is reported. The mechanism by which 16and 26are obtained is presumed to involve the intermediate formation of the 16‐electron (η6‐benzene)RuPMes* phosphinidene complex.

Novel, very stable ruthenium and osmium containing terminal phosphinidene complexes [(η⁶-Ar)(L)M&dbond;PMes*] (Ar=benzene, p-cymene; L=PR3, CO, and RNC) have been prepared by dehydrohalogenation of novel [(η⁶-Ar)MX2(PH2Mes*)] complexes in the presence of a stabilizing ligand. Xray crystal structures are reported for [(η⁶-C6H6)(PPh3)Ru&dbond;PMes*] (9) and [(η⁶-pCy)(PPh3)Os&dbond;PMes*] (4). Dehydrohalogenation in the absence of a stabilizing ligand resulted in the new Pspiroannulated Ru2P2-ring structure 16. Dehydrohalogenation in the presence of but-2-yne gave a novel phosphaallyl complex [(η⁶-Ar)Ru(η³-R2PC(Me)CHMe)] 26, for which an Xray crystal structure is reported. The mechanism by which 16 and 26 are obtained is presumed to involve the intermediate formation of the 16-electron (η⁶-benzene)Ru&dbond;PMes* phosphinidene complex.

Heating the nonchelating cis-bis-7-phosphanorbornadiene-[Mo(CO)4] complex (13) results in the thermal decomposition of one of the 7-phosphanorbornadiene groups. The phosphinidene thus generated adds intramolecularly to a C=C bond of the other ligand to give the novel diphosphorus complex 14. This reaction constitutes a metal-template-directed synthesis. Likewise, the intramolecular phosphinidene addition to the C=C bond of a Mo-phospholene ligand affords the diphos complex 18. Its crystal structure exhibits an extremely small P-Mo-P bite-angle for a five-membered chelate ring. The similar intramolecular 1,2-addition to a C=C bond of a phosphole ligand gives a highly strained, unstable intermediate product. Scission of its P−Mo bond generates a free coordination site, which is then occupied by either CO or a phosphole to yield complexes 22 and 23, respectively. The analogous intermolecular addition of [PhPW(CO)5] to a [phosphole-W(CO)5] complex gives the di-[W(CO)5] complexed adduct 28. The directing effect of the metal on the intra- and intermolecular additions is discussed.

Heating the nonchelating cis‐bis‐7‐phosphanorbornadiene‐[Mo(CO)4] complex (13) results in the thermal decomposition of one of the 7‐phosphanorbornadiene groups. The phosphinidene thus generated adds intramolecularly to a C=C bond of the other ligand to give the novel diphosphorus complex 14. This reaction constitutes a metal‐template‐directed synthesis. Likewise, the intramolecular phosphinidene addition to the C=C bond of a Mo‐phospholene ligand affords the diphos complex 18. Its crystal structure exhibits an extremely small P‐Mo‐P bite‐angle for a five‐membered chelate ring. The similar intramolecular 1,2‐addition to a C=C bond of a phosphole ligand gives a highly strained, unstable intermediate product. Scission of its P−Mo bond generates a free coordination site, which is then occupied by either CO or a phosphole to yield complexes 22and 23, respectively. The analogous intermolecular addition of [PhPW(CO)5] to a [phosphole‐W(CO)5] complex gives the di‐[W(CO)5] complexed adduct 28. The directing effect of the metal on the intra‐ and intermolecular additions is discussed.

The terminal phosphinidene complex PhPW(CO)5 adds to the imine bond of PhHC=N−Ph to give 3-membered ring azaphosphiridines, which undergo ring-expansion with an additional imine to yield a set of four isomeric five-membered ring diazaphospholanes. Treatment with the diimines PhHC=N-(CH2)n-N=CHPh (n=2,3,4) results instead—in all three cases—in only a single isomer of the (CH2)n bridged diazaphospholane. For n=2 or 3, this aminal group is easily hydrolyzed to afford new 6- and 7-membered ring heterocycles. No intermediate azaphosphiridine complex is observed during the addition reaction to the diimines. B3LYP/6–31G* calculations on an unsubstituted, uncomplexed system suggest that the initially formed P,N-ylide of the H2C=N-(CH)2-N=CH2 diimine both kinetically and thermodynamically favors an intramolecular 1,3-dipolar cycloaddition over an imine insertion into the CPN ring of an intermediate azaphosphiridine. Single-crystal X-ray structures for the (CH2)2-bridged azaphospholane complex and the HCl adduct of the 7-membered hydrolysis product are presented.

The terminal phosphinidene complex PhPW(CO)5 reacts with 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene to give two unexpected multicyclic organophosphorus compounds. One of them results from an initial 1,2-addition, followed by an intramolecular rearrangement. B3LYP/6–31G* calculations on simplified parent systems suggest that the reaction follows a unique concerted reaction pathway. The second, and major, product is a tetraphosphaquadricyclane derivative, which presumably results from an intramolecular [2+2] cycloaddition of an intermediate tetraphosphanorbornadiene complex. Single-crystal X-ray structures are presented for both products.

The terminal phosphinidene complex PhPW(CO)5adds to the imine bond of PhHC=N−Ph to give 3‐membered ring azaphosphiridines, which undergo ring‐expansion with an additional imine to yield a set of four isomeric five‐membered ring diazaphospholanes. Treatment with the diimines PhHC=N‐(CH2)n‐N=CHPh (n=2,3,4) results instead—in all three cases—in only a single isomer of the (CH2)nbridged diazaphospholane. For n=2 or 3, this aminal group is easily hydrolyzed to afford new 6‐ and 7‐membered ring heterocycles. No intermediate azaphosphiridine complex is observed during the addition reaction to the diimines. B3LYP/6–31G* calculations on an unsubstituted, uncomplexed system suggest that the initially formed P,N‐ylide of the H2C=N‐(CH)2‐N=CH2diimine both kinetically and thermodynamically favors an intramolecular 1,3‐dipolar cycloaddition over an imine insertion into the CPN ring of an intermediate azaphosphiridine. Single‐crystal X‐ray structures for the (CH2)2‐bridged azaphospholane complex and the HCl adduct of the 7‐membered hydrolysis product are presented.

The terminal phosphinidene complex PhPW(CO)5reacts with 2,4,6‐tri‐tert‐butyl‐1,3,5‐triphosphabenzene to give two unexpected multicyclic organophosphorus compounds. One of them results from an initial 1,2‐addition, followed by an intramolecular rearrangement. B3LYP/6–31G* calculations on simplified parent systems suggest that the reaction follows a unique concerted reaction pathway. The second, and major, product is a tetraphosphaquadricyclane derivative, which presumably results from an intramolecular [2+2] cycloaddition of an intermediate tetraphosphanorbornadiene complex. Single‐crystal X‐ray structures are presented for both products.

Kinetics of Lewis base(LB) complexed primary and secondary σ‐alkyllithiums (RLi) with triphenylmethane (TPMH) are reported. Among the properties investigated are the effective reaction orders (see diagram), precomplexation and mechanism, and relative reactivities of tetrameric and dimeric RLis, both for primary and secondary R.

Dimers both in the crystalline state and in solution: Lithium amides 1aand 2(NLi/N(Me)R = 1/2) are present as dimers (1a)2and 22in the crystalline state and, presumably with the same structures, in toluene and in THF. Lithium amide 3a(NLi/NMe2= 1/1) prevails in THF as the disolvated monomer 3a⋅2 THF. All three amides are broken down into solvent‐separated ions pairs by HMPA.